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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Visual scanning behavior and mental workload in aircraft pilots

This paper describes an experimental paradigm and a set of preliminary results which demonstrate a relationship between the level of performance on a skilled man-machine control task, the skill of the operator, the level of mental difficulty induced by an additional task imposed on the basic control task, and visual scanning performance. During a constant, simulated piloting task, visual scanning of instruments was found to vary as a function of the level of difficulty of a verbal loading task. The average dwell time of each fixation on the pilot's primary instrument increased as a function of the loading. The scanning behavior was also a function of the estimated skill level of the pilots, with novices being affected by the loading task much more than experts. The results suggest that visual scanning of instruments in a controlled task may be an indicator of both workload and skill.

Tole, J. R.↗
NASA NTRS1982

The evolution of an impact-generated atmosphere

The minimum impact velocities and pressures required to form a primary H2O atmosphere during planetary accretion from chondritelike planetessimals are determined by means of shock wave and thermodynamic data for rock-forming and volatile-bearing minerals. Attenuation of impact-induced shock pressure is modelled to the extent that the amount of released water can be estimated as a function of projectile radius, impact velocity, weight fraction of target water, target porosity, and dehydration efficiency. The two primary processes considered are the impact release of water bound in such hydrous minerals as serpentine, and the subsequent reincorporation of free water by hydration of forsterite and enstatite. These processes are described in terms of model calculations for the accretion of the earth. It is concluded that the concept of dehydration efficiency is of dominant importance in determining the degree to which an accreting planet acquires an atmosphere during its formation.

Lange, M. A.↗
NASA NTRS1981

Visual scanning behavior and pilot workload

An experimental paradigm and a set of results which demonstrate a relationship between the level of performance on a skilled man-machine control task, the skill of the operator, the level of mental difficulty induced by an additional task imposed on the basic control task, and visual scanning performance. During a constant, simulated piloting task, visual scanning of instruments was found to vary as a function of the level of difficulty of a verbal mental loading task. The average dwell time of each fixation on the pilot's primary instrument increased as a function of the estimated skill level of the pilots, with novices being affected by the loading task much more than the experts. The results suggest that visual scanning of instruments in a controlled task may be an indicator of both workload and skill.

Harris, R. L., Sr.↗
NASA NTRS1983

A method of predicting the performance deterioration of a compressor cascade due to sand erosion

Performance deterioration due to sand erosion is a well known phenomena for aircraft engines operating in particulate flow environments. A method for predicting this performance deterioration is developed and applied to a two dimensional compressor cascade. The locations of the particles impacts are computed by analyzing the trajectories of the individual particles. From this analysis, the material removed, the changes in the airfoil shape, and the roughness development over the surface are estimated as a function of time. The resulting airfoil profiles are analyzed for predicting performance by using an inviscid-viscous interaction technique. The analytical solution is compared with experimental results.

Balan, C.↗
NASA NTRS1983

Earth's magnetic field as a radiator to detect cosmic ray electrons of energy greater than 10 to the 12th eV

Synchrotron emission by a high-energy electron in the geomagnetic field and its dependence upon different arrival directions over Palestine, Texas, where major balloon-borne experiments are being conducted, is studied. The dependence of detector response on the arrival direction of electron, the different criteria which are adopted to identify an electron event, the area of the detector, and the energy of the electron are discussed. An omnidirectional circular detector is used to examine whether it is possible to determine the energy of an electron without knowing its arrival direction. The collecting power of a detector is estimated as a function of the energy of electrons for different detector areas with different selection criteria, and this information is used to calculate the event rates expected by folding in the energy spectrum of cosmic ray electrons to show the viability of detecting cosmic ray electrons at energies greater than a few TeV.

Balasubrahmanyan, V. K.↗
NASA NTRS1984

Estimation of discontinuous coefficients in parabolic systems: Applications to reservoir simulation

Spline based techniques for estimating spatially varying parameters that appear in parabolic distributed systems (typical of those found in reservoir simulation problems) are presented. The problem of determining discontinuous coefficients, estimating both the functional shape and points of discontinuity for such parameters is discussed. Convergence results and a summary of numerical performance of the resulting algorithms are given.

Lamm, P. D.↗
NASA NTRS1985

Planetary Interior Modeling and Tectonic Implications

A technique is described for estimating spectral admittance functions using Pioneer Venus gravity and topography data. These admittance functions provide a convenient means to carry out systematic geophysical studies over much of the surface of Venus with a variety of interior density models. The admittance functions are calculated in the observation space of line-of-sight (LOS) gravity. Both closed and open system petrological models are considered for the Tharsis region of Mars. An analytic theory for isostatic compensation on one-plate planet is applied, including membrane stresses in the lithosphere, self gravitation, and rotational ellipticity. Crucial to this stress modeling and also to the petrological modeling is the observation that the earliest fracturing seen in the Tharsis region is associated with isostatic stresses. The radial fractures that extend far from Tharsis are associated with an additional and/or a completely different mechanism.

Phillips, R. J.↗
NASA NTRS1985

A potential-energy surface study of the 2A1 and low-lying dissociative states of the methoxy radical

Accurate, ab initio quantum chemical techniques are applied in the present study of low lying bound and dissociative states of the methoxy radical at C3nu conformations, using a double zeta quality basis set that is augmented with polarization and diffuse functions. Excitation energy estimates are obtained for vertical excitation, vertical deexcitation, and system origin. The rate of methoxy photolysis is estimated to be too small to warrant its inclusion in atmospheric models.

Jackels, C. F.↗
NASA NTRS1986

Infrasonic emissions from local meteorological events: A summary of data taken throughout 1984

Records of infrasonic signals, propagating through the Earth's atmosphere in the frequency band 2 to 16 Hz, were gathered on a three microphone array at Langley Research Center throughout the year 1984. Digital processing of these records fulfilled three functions: time delay estimation, based on an adaptive filter; source location, determined from the time delay estimates; and source identification, based on spectral analysis. Meteorological support was provided by significant meteorological advisories, lightning locator plots, and daily reports from the Air Weather Service. The infrasonic data are organized into four characteristic signatures, one of which is believed to contain emissions from local meteorological sources. This class of signature prevailed only on those days when major global meteorological events appeared in or near to eastern United States. Eleven case histories are examined. Practical application of the infrasonic array in a low level wing shear alert system is discussed.

Zuckerwar, A. J.↗
NASA NTRS1986

Collision strengths for the intercombination lines of S III

The collision strengths of intercombination lines of S III ions observed in the Io torus are calculated on the basis of data gathered by Voyager instruments, the IUE and the Faint Object Telescope. The doubly ionized ions are excited by electron impacts and move from the 3P2P(3) ground state to excited 3s3P3(1)PO, (1)DO, 3p3d(1)PO, and 3p4s(1)PO states. Excitational cross sections are calculated with a two-state close-coupling approximation for the energy range up to 1,000,000 K, with target states being represented by multiconfiguration interaction wave functions. The close-coupling approximation regarded as an accurate technique because of the dominance of the Coulomb factor in the ionized state. The wave function calculations are estimated to yield values accurate to within 30 percent. Further work is need to quantify the magnitude of error introduced by resonance contributions to the collision strengths.

Ho, Y. K.↗
NASA NTRS1986

Oxidation of commercial purity titanium

The oxidation kinetics of commercial purity Ti-A55 exposed to laboratory air in the 593-760 C temperature range were continuously monitored by thermogravimetric analysis. The oxide thickness was measured by microscopy, and the substrate contamination was estimated from microhardness measurements. The microhardness depth profiles were converted to oxygen composition profiles using calibration depth. The oxygen diffusion coefficient in alpha-Ti appears to be approximately concentration-independent in the 1-10 at. pct oxygen range. Diffusion coefficient for oxygen in TiO2 has been estimated as a function of temperature and is found to be about 50 times the value in alpha-Ti. The metallographically prepared cross sections of the oxidized specimens revealed a 'moving boundary' in the substrate, parallel to the oxide-metal interface. This boundary was associated with a specific oxygen level of 5.0 + or - 0.5 at. pct. It occurred at a distance from the oxide-metal interface which was correlatable with temperature and time of exposure. The diffusion coefficient corresponding to the composition of this moving boundary is in excellent agreement with the effective diffusion coefficient for the substrate contamination.

Unnam, J.↗
NASA NTRS1987

Estimation of discontinuous coefficients in parabolic systems - Applications to reservoir simulation

Spline-based techniques for estimating spatially varying parameters that appear in parabolic distributed systems (typical of those found in reservoir simulation problems) are presented. In particular, the problem of determining discontinuous coefficients is discussed, estimating both the functional shape and points of discontinuity for such parameters. In addition, the ideas may also be applied to problems with unknown initial conditions and unknown parameters appearing in terms representing external forces. Convergence results and a summary of numerical performance of the resulting algorithms are given.

Lamm, Patricia K.↗
NASA NTRS1987

On the 1A1 - 3B1 separation in CH2 and SiH2

The 1A1 - 3B1 separation in CH2 and SiH2 has been computed using extended basis sets and CASSCF/SOCI wave functions. Using theoretical estimates for the effects of zero-point vibration yields T(0) values of 8.9 and -20.9 kcal/mol respectively, in excellent agreement with the experimental values of 9.02 and -21.0 kcal/mol. A corollary to the small zero-point vibrational contribution to the separation is that the symmetric stretching fundamental in CH2(3B1) must be near 3100/cm, much less than a recently suggested value of around 3400/cm. An accurate Te value for SiH2 establishes the ionization potential of the 1A1 state as 9.15 eV, the higher of two recent experimental values.

Bauschlicher, Charles W., Jr.↗
NASA NTRS1987

Quantum fluctuations of the superconducting cosmic string

Quantum fluctuations of the proposed superconducting string with Bose charge carriers are studied in terms of the vortices on the string world sheet. In the thermodynamical limit, it is found that they appear in the form of free vortices rather than as bound pairs. This fluctuation mode violates the topological conservation law on which superconductivity is based. However, this limit may not be reached. The critical size of the superconducting string is estimated as a function of the coupling constants involved.

Zhang, Shoucheng↗
NASA NTRS1988

The versatility of a truss mounted mobile transporter for in-space construction

The Mobile Transporter (MT) evolution from early erectable structures assembly activities is detailed. The MT operational features which are required to support astronauts performing on-orbit structure construction or spacecraft assembly functions are presented and discussed. Use of the MT to perform a variety of assembly functions is presented. Estimated EVA assembly times for a precision segmented reflector approximately 20 m in diameter are presented. The EVA/MT technique under study for construction of the reflector (and the entire spacecraft) is illustrated. Finally, the current status of development activities and test results involving the MT and Space Station structural assembly are presented.

Bush, Harold G.↗
NASA NTRS1990

The versatility of a truss mounted mobile transporter for in-space construction

The Mobile Transporter (MT) evolution from early erectable structures assembly activities is detailed. The MT operational features which are required to support astronauts performing on-orbit structure construction or spacecraft assembly functions are presented and discussed. Use of the MT to perform a variety of assembly functions is presented. Estimated EVA assembly times for a precision segmented reflector approximately 20 m in diameter are presented. The EVA/MT technique under study for construction of the reflector (and the entire spacecraft) is illustrated. Finally, the current status of development activities and test results involving the MT and Space Station structural assembly are presented.

Bush, Harold G.↗
NASA NTRS1985

Bearing Tester Data Compilation Analysis, and Reporting and Bearing Math Modeling

The magnitude and direction of fluid induced torques and forces on the 57 mm bearing cage is considered to be a contributing factor in possible cage instabilities that can produce intermittent high heating in the bearing. Analyses of the fluid forces and torques are presented. Heat generated by viscous fluid work was estimated for two flow diverter configurations and a coolant flow of 10 lbs/sec to support the thermal evaluation of the LOX Bearing Materials Tester. Results of the analysis of the LOX turbopump turbine end bearings are discussed. Coolant velocities for the no. 4 LOX turbopump turbine end bearings were estimated as a function of shaft speed and coolant flow rate. Contact angles and track width data were developed for the 57 mm bearing as functions of shaft speed, and axial and radial loads. The Advanced Dynamics of Rolling Elements (ADORE) computer program was installed on the MSFC UNIVAC 1100 and a test case successfully run. Both the text output and the plotting output were verified. The Bearing Seal and Materials Tester - Test Condition Data Base was developed. The parametric analysis of the operating characteristics of the LOX turbopump pump end bearing using the 45 mm bearing thermal model was begun.

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